Object-Relation Model of ORACLE Spatial Database: with Discussion of RDB and OODB Application in GIS

There are some problems of RDB in GIS application. Sometimes the data type is too simple to describe non-structured or complex-structured data in GIS and the simple model can't express the relation of hierarchy, inheritance, aggregation, generalization or specialization, or there is impedance mismatch between SQL and programming language, especially the current popular object-oriented language. While object-oriented (OO) technology may be useful to solve these problems. ORACLE spatial database extends the traditional relation database with the technology, the so-called object-relation model, which features adding to RDB an object data type named SDO-GEOMETRY to store geometry. An application example of ORACLE spatial database demonstrated the advantages of OODB in describing spatial data and the efficiency in expressing compound object and processing spatial data compared to RDB which only stores meaningless data. Certainly, there are still some issues that need further research in OODB: which direction OODB will develop: pure OODB or object-relation DB, the data model match between RDB and OODB, the mathematic basis and formalization for OODB and how to take advantages of existing mature technologies of RDB such as transaction control, integrity check, data reproduction in the development of OODB.